think3D, one of India’s largest 3D printing company, recently helped the Indian Navy to produce quick replacement parts of centrifugal pump impellers on-board its ships. The 3D printed parts resolve the Navy’s long pending need for rapid replacement of critical components.
Impeller Problem
The Indian Navy has been trying to solve one of its major problems of frequent impeller breakdowns due to displacement of the eye of impeller during rotation and due to foreign particles in the sea hitting the impeller. This is a common occurrence esp. when these impellers rotate at high speeds for longer time periods. Replacement parts for these impellers have to be manufactured using sand casting process and it takes around 3 months turn-around time to manufacture a new impeller. Each ship has multiple such pumps and thus multiple such impellers and constant breakdowns of these are creating a major impediment to Navy in carrying out their regular tasks.
Navy was looking for an alternative solution to its problem where the impellers can be produced quickly and at a lower cost of ownership.
The Vizag Navy reached out to the Vizag-based think3D with a hope of finding a solution to their problem. think3D team spent few days with the Navy team to understand the problem statement in detail, visited the ships to see in real various forces acting on the impellers and collected few data sheets on material properties required and boundary conditions. Based on the initial discussions, think3D took on the project.
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The project started with 3D scanning of the existing impeller. The scanned data was cleaned up and used to recreate the CAD model of the impeller. The scanned data needs to be cleaned up before it is of any use and so once the CAD model was ready the next obvious step was to perform FEA analysis of the impeller by using the boundary conditions and changing the material properties to see which material and which 3D printing process best fits the bill. Various materials like nylon composites, glass filled nylon, PA12, other regular plastics were tested for suitability.
One most important requirement for the impeller material is damping property. Damping is the ability of the material to convert vibrational energy into other forms of energy (generally heat) without the part breaking apart. Also, the part should have elasticity to withstand the vibrations. This ruled out various high strength materials as they are highly brittle. The actual material was finalized on this particular criterion of having good damping property and elasticity.
CAD Data Modification
In the pump design, a metal rod is inserted into the eye of the impeller and this metal rod gives the impeller the required torque for rotating the impeller. Since the material is of plastic, metal rod shall quickly eat away the part. To avoid this issue additional material was added at the eye of the impeller. This additional material will be then machined in CNC and metal bushings will be inserted.
3D Printing of Impeller
think3D used Hp’s MultiJet Fusion (MJF) technology to 3D Print the part. The settings were thoroughly analysed and modified to print the part with desired mechanical properties. The part was then CNC machined and metal bushing was inserted to create an interface between metal rod and plastic component. The 3D printed part then was passed through multiple tests in the real environment and the Navy was satisfied with the results.
3D printing substantially reduced the time to manufacture the part to just two days. In traditional case, the same part would have taken close to 3 months to manufacture. Additionally the total cost of ownership is 40% lower for 3D Printed part compared to the traditionally manufactured part. Another add-on benefit of 3D printing is that the impeller is lighter in weight than the traditionally manufactured one. The actual metal impeller used to weight 9 kilograms (approximate) whereas the 3D printed impeller weighed just 1 kg. This reduction in weight would result in better fuel efficiency of the ship.
What’s Next?
With the successful completion of 3D Printed impeller, think3D is now building a digital repository of impellers for Indian Navy. Once the repository is built, think3D shall 3D Print the required impeller on demand and supply to the Navy, a supply chain management process unforeseen so far for physical goods.
Conclusion
This case study perfectly illustrates how 3D printing coupled with 3D scanning can be highly beneficial for organizations in multiple departments. Spare parts management is a major cost component for many organizations. With 3D Scanning, a digital repository of spare parts can be maintained and the required component can be printed on demand leading to huge cost savings. Secondly, companies can easily develop lower cost alternatives to the existing parts.
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